US3600633A - Safety device for office machines actuated by an electric motor consisting of a temperature responsive deformable thermoplastic gear - Google Patents

Safety device for office machines actuated by an electric motor consisting of a temperature responsive deformable thermoplastic gear Download PDF

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Publication number
US3600633A
US3600633A US46785A US3600633DA US3600633A US 3600633 A US3600633 A US 3600633A US 46785 A US46785 A US 46785A US 3600633D A US3600633D A US 3600633DA US 3600633 A US3600633 A US 3600633A
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US
United States
Prior art keywords
gear
motor
temperature
machine
shaft
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US46785A
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English (en)
Inventor
Carlo Bellis
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Olivetti SpA
TIM SpA
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Olivetti SpA
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Filing date
Publication date
Application filed by Olivetti SpA filed Critical Olivetti SpA
Application granted granted Critical
Publication of US3600633A publication Critical patent/US3600633A/en
Anticipated expiration legal-status Critical
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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/10—Structural association with clutches, brakes, gears, pulleys or mechanical starters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/10—Structural association with clutches, brakes, gears, pulleys or mechanical starters
    • H02K7/116—Structural association with clutches, brakes, gears, pulleys or mechanical starters with gears
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T74/00—Machine element or mechanism
    • Y10T74/19—Gearing
    • Y10T74/19614—Disconnecting means

Definitions

  • a safety device for electric office machines comprises a reduction gear train adapted to transmit the rotation of the motor shaft to a main shaft of the machine, the gear train comprising a gear of thermoplastic material.
  • the gear train comprising a gear of thermoplastic material.
  • the present invention relates to 'a safety device for typewriters, adding machines, calculators'and similar office machines actuated by an electric motor, comprising a reduction gear adapted to transmit the rotation of the driving shaft to a main shaft of the machine.
  • the safety device is constituted by a disc-type clutch interposed'between the drivihg shaft and the mainv shaft of the machine.
  • the discs of the friction clutch sliprelative to-one another in the event" of accidental jamming of the main shaft'of the' machinecaused, for example, by breakingor deformation of a part, thus enabling the motor to rotate without stalling.
  • the disc-type clutch hasthe disadvantage of requiring constant checking of its calibration, this being considerably affected by the ambienttemperature,.the presence of foreign bodies between'the'discs and the use of the machine. 1
  • the disc-type clutch is relatively costly, especially if fitted to simple office machines such as-addingmachines, and cannot be fitted to machines actuated by shaded-polemotors, which are adapted to supply at the start atorque smaller than that supplied by an induction motor of equaldimensions.
  • shaded-pole electric motor being stalled,.itis generally not able to supply a torque sufficient tocause the discs of a friction clutch to slip, nor is it ableto absorb a current which will'trip an automatic switch withcertainty.
  • Another known safety device is constituted by a' maximumcurrent switch, which is disposed in series in the supply circuit of the electric motor for the purpose of breaking the circuit automatically in the event of consumption of a current greater than the normal current, for example owingto the arrest of the motor due to jamming of the mainshaft of the machine.
  • This device is also costly and its range of application is preferably limited to typewriters and accounting machines and not to simple adding machines.
  • th'eautomatic switch has the drawback that it may also trip inappropriately in the case of sudden variations in the mains voltage.
  • the object of the present invention is to provide a safety A device which can be used for typewriters, adding machines or calculators actuated by a shaded-pole electric motor, the cost of which is substantially lower than that of conventional induction motors.
  • the device intervenes in the event of jamming of the machine to protect the motor before the insulation of the motor winding is jeopardized, but the cost of the device can be low and the replacement thereof can be extremely simple.
  • asafety device for' a typewriter, adding machine, calculator or other office machine actuated by an electric motor comprising an electric motor, a reduction gear train adapted to transmit the rotation of the motor shaft to a main shaft of the machine, the gear train comprising a first gear of thermoplastic material in mesh with a second gear, means being provided for rendering the temperature of the second gear a direct function of the temis stalled and the rotor temperaturerises, the temperature of thesecondgear rises sufficiently rapidly to cause the teeth of the first'gear to become plastic in consequence of jamming of the main shaft of the machine'and allow the motor to turn freely before real damage occurs thereto.
  • An electric motor I of an adding machine is fixed to the 5 machine by means of a bracket 2 fixed by two bolts 3 to one side'4' of the frame of the machine and by two screws 5 to the motor I.
  • the motor I is normally stationary but can be set in rotation, in manner known per se, as a result of the depression ofa start key of the machine which is not shown in thedraw-
  • the motor I includes a number of short-circuited turns 6 and a stator winding 7 and also a squirrel cage rotor 8 fast with a metal shaft 9 having a high thermal conductivity. At one end of the shafi 9 there is fixed a metal pinion 10.
  • This pinion is in mesh with a toothed wheel 1 1' of thermoplastic material which is adapted to rotate on a spindle 12 fixed to the frame of the machine.
  • a pinion 14 is integral with the wheel 11 and is in tum in mesh with a toothed wheel 15 fixed to a shaft 16. This shaft constitutes the main shaft of the machine and rotates in a bearing inthe side frame 4.
  • the device operates in the following manner.
  • the rotor 8 is also jammed, with the result that from this instant the currents induced therein causes an increase in the temperature of the rotor itself.
  • the shaft 9 and the pinion 10 also rise in-temperature if the jamming of the machine persists. If the operator does not become aware of the jamming and does not interrupt the supply to the motor I, the temperature of the rotor 8, the shaft 9 and the pinion I0 continues to rise.
  • the temperature of the pinion It may reach" a value of about 170 C. in a time of the order of 20 to 30 seconds.
  • the winding 7 which, with the rotor jammed, consumes a current a little greater than the current normally consumed, increases its temperature without, however, reaching values harmful to the insulation of the winding itself.
  • the temperature of 170 C. reached by the pinion 10 is sufficient to make the teeth of the wheel I l with which the pinion is in mesh plastic, with the result that the rotor 8 can turn again, thus avoiding the winding 7 of the motor being damaged by any further increase in its temperature.
  • the thickness of the wheel I I and the pitch of its teeth By suitably dimensioning the thickness of the wheel I I and the pitch of its teeth and choosing a suitable material with which to form the wheel 11, it is possible to be certain of renderingthe teeth of the wheel plastic at the instant when the pinion I0 reaches a fixed temperature. If the jamming of the machine lasts for less that the fixed time, the teeth of the wheel II do not have time to become plastic and the machine is therefore able to resume operation. 0n the other hand, if the teeth of the wheel 11 in mesh with the pinion I0 do become plastic, it is extremely simple to effect replacement of the wheel II after eliminating the cause which produced the jamming of the machine. In fact, it is sufficient to slip the wheel 11 off the spindle I2 and place a new wheel thereon.
  • a device wherein the motor shaft is a metal shaft which is fast with the rotor and with the second gear.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Connection Of Motors, Electrical Generators, Mechanical Devices, And The Like (AREA)
  • Manufacture Of Motors, Generators (AREA)
  • Gears, Cams (AREA)
  • Transmission Devices (AREA)
US46785A 1969-06-21 1970-06-16 Safety device for office machines actuated by an electric motor consisting of a temperature responsive deformable thermoplastic gear Expired - Lifetime US3600633A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
IT5233069 1969-06-21

Publications (1)

Publication Number Publication Date
US3600633A true US3600633A (en) 1971-08-17

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ID=11276775

Family Applications (1)

Application Number Title Priority Date Filing Date
US46785A Expired - Lifetime US3600633A (en) 1969-06-21 1970-06-16 Safety device for office machines actuated by an electric motor consisting of a temperature responsive deformable thermoplastic gear

Country Status (6)

Country Link
US (1) US3600633A (en, 2012)
JP (1) JPS4827860B1 (en, 2012)
CH (1) CH512849A (en, 2012)
DE (1) DE2030869A1 (en, 2012)
FR (1) FR2047007B1 (en, 2012)
GB (1) GB1283132A (en, 2012)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3872334A (en) * 1972-04-14 1975-03-18 Robert J Loubier Integral rotor and gear assembly
US6037685A (en) * 1999-02-12 2000-03-14 Shop-Vac Corporation Thermal protection apparatus for electric motors
US6184601B1 (en) 1999-02-24 2001-02-06 Shop Vac Corporation Thermally responsive protection apparatus
US20190036418A1 (en) * 2015-12-23 2019-01-31 Siemens Aktiengesellschaft Permanent-Magnet Synchronous Machine with Automatic Rotor Decoupling in the Winding Short Circuit

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2314227A (en) * 1940-11-08 1943-03-16 Sulzer Ag Coupling for transmitting torques
US3441820A (en) * 1967-08-18 1969-04-29 Gen Time Corp Timing system having electromechanical oscillator with fail-safe improvement

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2314227A (en) * 1940-11-08 1943-03-16 Sulzer Ag Coupling for transmitting torques
US3441820A (en) * 1967-08-18 1969-04-29 Gen Time Corp Timing system having electromechanical oscillator with fail-safe improvement

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3872334A (en) * 1972-04-14 1975-03-18 Robert J Loubier Integral rotor and gear assembly
US6037685A (en) * 1999-02-12 2000-03-14 Shop-Vac Corporation Thermal protection apparatus for electric motors
US6184601B1 (en) 1999-02-24 2001-02-06 Shop Vac Corporation Thermally responsive protection apparatus
US20190036418A1 (en) * 2015-12-23 2019-01-31 Siemens Aktiengesellschaft Permanent-Magnet Synchronous Machine with Automatic Rotor Decoupling in the Winding Short Circuit

Also Published As

Publication number Publication date
FR2047007B1 (en, 2012) 1973-01-12
DE2030869A1 (en, 2012) 1970-12-23
FR2047007A1 (en, 2012) 1971-03-12
JPS4827860B1 (en, 2012) 1973-08-27
GB1283132A (en) 1972-07-26
CH512849A (it) 1971-09-15

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